Adsorption of Silver from Aqueous Solution with High Capacity and Selectively by Using Ag plus Imprinted Polymeric Nanoadsorbent

The selective separation of precious metals from complex aqueous solutions is important in protecting the environment, aquatic ecosystems, water resources and recycling resources. In this study, cysteine-containing polymeric nanoparticles were synthesized using the molecular imprinting (MIP) technique with the mini-emulsion polymerization method. The basis of the polymer design is inspired by affinity of silver to cysteine in biological systems. The synthesized silver ion imprinted (Ag⁺-IIP) poly(hydroxyethylmethacrylate-N-methacryloyl-L-cysteine) poly(HEMA-MAC) nanoparticles were characterized by elemental analysis, zeta sizer, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The effects of pH, ionic strength and interaction time on adsorption of Ag⁺ ions were investigated. In experimental studies, the highest adsorption amount (196.9 mg g^-1 nanoparticle) was reached in a short period of 40 min at pH 5.0 and 150 mg L^-1 concentration. Selectivity studies of synthesized Ag⁺-IIP nanoparticles against silver (Ag⁺) ions were carried out in the presence of lithium (Li⁺), barium (Ba²⁺), mercury (Hg²⁺) and cadmium (Cd²⁺) ions. Experimental results indicate that nanoparticles adsorb Ag⁺ ions with high selectivity. Ag⁺-IIP nanoparticles have 3.7, 3.1, 2.4, and 2.6 times more selective or higher affinity for Ag⁺ ions compared to Li⁺, Ba²⁺, Hg²⁺ and Cd²⁺ ions, respectively, compared to Ag⁺-non-imprinted (NIP) nanoparticles.